1. Filed of the Invention
The present invention relates to a sewing machine having a needle threading mechanism, which automatically threads a thread eye of a sewing needle.
2. Description of the Related Art
Conventional sewing machines have a plurality of thread passing parts (a thread tension regulator, a thread take-up spring, a thread take-up lever, a needle bar thread guide etc.), through which a needle thread extending from a thread spool is passed. After having been passed through the thread passing parts in a predetermined sequence and path, the needle thread is passed through a thread eye of a sewing needle attached to a needle bar. Also, some of the conventional sewing machines have an automatic needle threader having a thread retaining member and a threading member to retain the end of the needle thread in order to automatically pass the needle thread through the needle eye of the sewing needle. In the above sewing machine, when the needle thread is moved to a thread turnover position near the front of the thread eye of the sewing needle by the thread retaining member retaining the needle thread, the threading member aligned at the same height as the thread eye of the sewing needle rotates in the opposite direction and comes out of the thread eye to pass the needle thread through the needle eye.
On the other hand, sewing machines are provided with a vertically moving mechanism to switch a presser bar having a presser foot to an elevated position and lower position so that the presser foot does not become an impediment when replacing work cloth or adjusting a layout of work cloth. There are two types of vertically moving mechanisms: one of which switches the presser bar to the elevated position and the lowest position depending on user's operation of a presser foot lifting lever and the other, which automatically switches the position of the presser bar.
For example, JP-B-1993-59755 discloses a vertically moving device automatically switching the position of the presser bar. The vertically moving apparatus has two modes, namely, a manual operation mode and an automatic operation mode. In the automatic operation mode, the presser bar is moved to the elevated position predetermined by a servo solenoid. This enables efficient location and rotation of work cloth in a consecutive embroidery process, in which the type of work cloth does not change.
When an automatic threading mechanism is activated in the state, in which the presser bar is in the elevated position, a threading hook member of the automatic threading mechanism and the presser foot interferes with each other and the threading member may be damaged. Therefore, in case of performing needle threading by the threading mechanism in such a state, the user needs to operate a presser foot lifting lever to move the presser bar to the lower position. That is, even in the case of performing needle threading by the automatic threading mechanism, manual operation needs to be performed and it becomes difficult to improve an efficiency of the needle threading process.
Also, the elevating device set forth in the above-noted publication only automatically moves the presser bar to the predetermined elevated position and does not automatically move the presser bar in conjunction with the operation of the automatic threading mechanism. Therefore, in order to operate the automatic threading mechanism when the presser bar is in the elevated position, the user needs to operate the presser foot lifting lever and move the presser bar to the lower position.